This relates generally to resistive random access 5 memories (ReRAM).
ReRAM relies on materials that can be electrically switched between a higher conductive state and a lower conductive state several times. One type of ReRAM, a phase change memory, uses phase change materials, i.e., materials that may be electrically switched between a generally amorphous and a generally crystalline state. One type of phase change memory element utilizes a phase change material that may be, in one application, electrically switched between a structural state of generally amorphous and generally crystalline local order or between different detectable states of local order across the entire spectrum between completely amorphous and completely crystalline states.
A phase change memory element may be formed from a stack of layers including, for example, a chalcogenide layer, a heater, and electrode layers. During the etching of the individual memory elements from this stack, a relatively high aspect ratio structure results, made up of strips of materials defined by the stack. It is sometimes desirable to use a copper metal line for the bitline in order to reduce resistance, especially in relatively small feature sized technologies.